Stencil printing machine



y 8; 1957 w. CHILDERS STENCIL PRINTING MACHINE Filed July 19, 1955 4Sheets-Shem. l

- INVENTOR fives/v l ll ATTO R N EY y 8, 1957 w. CHILDERS STENCILPRINTING MACHINE 4 SheetsShee't 2 Filed July 19, 1955 m0 Wm kw l w MkMay 28, 1957 w. CHILDERS STENCIL PRINTING MACHINE 4 Sheets-Sheet 3 FiledJuly 19, 1955 Tlcll 1.

INVENTOR We? TJEIJU. /4/ L? May 28, 1957 w. CHILDERS 2,793,587

STENCIL PRINTING MACHINE Filed July 19, 1955 4 Sheets-Sheet 4 4 win/ m.3/

, INVENTQR fiei/v 6 674.05?!

ATTORNEY United States Patent STENCIL PRINTING MACHINE Warren Childers,Houston, Tex., assignor, by mesne assignments, to American Type FoundersCo., Inc., Elizabeth, N. 1., a corporation of Delaware Application July19, 1955, Serial No. 523,048

15 Claims. (Cl. 101124) This invention relates to printing methods andapparatus, and more particularly to a stencil printing machine.

The subject of the present invention is an apparatus which may beattached to a conventional reciprocating bed letter press, and comprisesa frame across which is stretched a stencil or silk screen adapted to bemoved past a rotary platen while ink is forced through the apertures inthe stencil to produce an image upon the paper mounted on the platen.The critical element of this type of device is the squeegee means forforcing ink through the apertures of the stencil. The disadvantage ofprior mechanisms have been attributable to the inability to obtainuniformity of pressure along the entire length of the squeegee againstthe stencil, thereby resulting in the printing of non-uniformimpressions.

In order to overcome the defects of prior art machines, I have devisednovel means for forcing the ink through the apertures of the stencil,and the salient feature of the invention is the provision of a flexiblesqueegee in the form of a hollow resilient or elastic tube which may beinflated as circumstances require for producing the requisite uniformpressure against the stencil or silk screen.

The provision for inflating and deflating the squeegee tube also permitsthe operating edge thereof to be retracted from the surface of thestencil during its return, nonprinting pass, thereby reducing frictionalwear upon the stencil by substantially fifty percent, and thereforevirtually doubling its life.

By reason of the fact that the squeegee tube is inflated, the pressureexerted by the squeegee is uniform along its entire length andconsequently ink will be urged uniformly through the entire width of thestencil or silk screen producing a uniform impression upon the printingpaper or print receiving fabric. This feature obviates the defects ofprior art machines whose mechanically supported squeegees have atendency to sag in their mid-sections, or which require special andcomplex mechanical support means. v

A pumping system is connected to the inflatable squeegee and a simplevalve is provided to diiferentiate between the pressure branch of thesystem, on the one hand, and the exhaust or relief branch, on the otherhand. The operation of the valve is coordinated with the motion of thestencil carriage reciprocating past the platen of the machine wherebythe squeegee tube is inflated during the printing pass of the stencilcarriage and deflated or relieved during the non-printing return pass ofthe carriage. In those embodiments where the squeegee tube is at leastpartially immersed in ink, the deflating action of the tube is arrangedto cause the ink to be transmitted toward the operative edge of thesqueegee whereby an immediate supply of ink is ensured at the beginningof the next printing pass of the stencil.

Still other objects and advantages of my invention will be apparent fromthe specification. V

The features of novelty which I believeto be characteristic of myinvention are set forth herein and will best be understood, both as totheir fundamental principles and as to their particular embodiments, byreference to the specification and accompanying drawings, in which:

Figure l is a schematic side elevation, partly in section, some partsbeing omitted, showing the reciprocating silk screen and its carrier inrelation to the printing platen, and the latching and valve mechanismtherefor, prior to the printing operation;

Fig. 2 is a view similar to Fig. 1, showing the apparatus in a positionsubsequent to the printing operation;

Fig. 3 is similar to Figs. 1 and 2, showing the apparatus during theprinting operation;

Fig. 4 is a top plan view of the apparatus shown in Figs. 1, 2 and 3,some parts being omitted, some parts broken away and some parts beingadded;

Fig. 5 is a section view taken on line 5-5 of Fig. 4;

Fig. 6 is a section view taken on line 6-6 of Fig. 4;

Fig. 7 is a greatly enlarged perspective and section view of the inktray and squeegee shown in Figs. 1 through 4;

Fig. 8 is a View showing a cross section of the squeegee and ink trayshown in Fig. 7 with the squeegee inflated;

Fig. 9 is similar to Fig. 8 and shows the squeegee in the deflatedposition;

Fig. 10 is a greatly enlarged schematic section view of the valvemechanism shown in Fig. 4, together with a schematic representation ofthe inflating and deflating pumping system, shown in position forinflating the squeegee;

Fig. -11 shows the valve mechanism of Fig. 10 in position for deflatingor relieving the squeegee;

Fig. 12 is a greatly enlarged perspective view of an alternativeembodiment of the squeegee;

Fig. 13 is a cross section view of the squeegee shown in Fig. 12 in theinflated printing position;

Fig. 14 is similar to Fig. 13, showing the squeegee in the deflatedposition, and showing the means for causing ink to flow toward and ontosaid squeegee; and

Fig. 15 is an elevation of the mechanism shown. in Fig. 12 in thedirection of the arrow.

Referring now to the drawings, and particularly to Figs. 1, 2 and 3,there is shown a horizontal stationary press bed 21 which is mountedupon the main frame (not shown) of any standard type of printingmachine. Slidably movable back and forth over the surface of the pressbed 21 is a substantially rectangular carriage 22 which is reciprocatedon the press by means (not shown) that are well known in the printingart. The forward end of carriage 22 has an upwardly extending shoulder23.

Positioned above carriage 22 is any standard type of rotary platen 24which carries the paper or other print receiving surface and which isadapted to be rotated in the direction of the arrow by suitablemechanisms (not shown) coordinated with the reciprocating motion ofcarriage 22, said mechanisms being well known in the printing art,therefore obviating the necessity for providing a further descriptionthereof.

Mounted on surface 25 of carriage 22 is a substantially rectangularframe, generally designated 26, said frame being connected to carriage22 and moving therewith in a reciprocating path. Frame 26 comprises aforward bar 27, a rearward bar 28, and side bars 29 .and 30. Frame 26may be provided with a floor 31 of sheet metal or the like, whereby theframe may, in some embodiments, perform the function of an ink tray.Floor 31 may have upwardly extending flanges 32 extending into suitablegrooves in bars 27, 28, 29 and 39 (Figs. 4- and 5) in order to preventleakage of ink. In other embodiments carriage 22 may be provided with apair of longitudinal upwardly extending guide rails 35 (Figs. 4 and 5)for stabilizing the reciprocating motion of frame 26.

Stretched over frame 26 is a stencil 36, which may be in the form of asilk screen or the like, the edges of which are folded downward over theexternal walls of the frame and secured thereto by means of suitablepins 37, or the like. (See Fig. 4.)

Positioned transversely within frame 26 and below stencil 27 is anelongated inking assembly, generally designated 41, which is movablelongitudinally within frame 26, and at times, independently of themotion of said frame. Inking assembly 41 contains the stencilling orprinting ink and also supports a squeegee Whose upper edge is adapted toforce ink through the pores or openings in the stencil onto the papercarried by platen 24. The structural details of the squeegee will bedescribed hereinbelow.

Connected to the rearward portion of ink assembly 41 are a pair ofrearwardly extending guide tubes 42 and 43 whose rearward ends extendthrough the rearward bar 28 of frame 26. The rearward ends of tubes 42and 43 telescopically accommodate guide rods 44 and 45, respectively,the rearward ends of said rods being rigidly secured by suitable meansto the upwardly extending flange 47 of bracket 48 attached to press bed21.

A transversely positioned slide bar 51 has a pair of apertures whichslidably accommodate guide bars 44 and 45, said bar being normally urgedforwardly from flange 47 by means of springs 52 coiled around guide bars44 and 45.

Mounted by welding or otherwise upon guide tubes 42 and 43 are brackets55 and 56 having upwardly extending arms 57 and 53, respectively.Extending through arms 57 and 58 is a rotatable rod 61 at the ends ofwhich are mounted pivotable latches 62 and 63 adapted to engage anddisengage hooks 64 and 65, respectively, attached to slide bar 51.Latches 62 and 63 are normally maintained in engagement with hooks 64and 65, respectively, by springs 67, shown in Figs. 1, 2, 3 and 4, butomitted from Fig. 6 for the sake of clarity of illustration.

Connected between brackets 55 and 56, on the one hand, and bar 51 on theother, are springs 68 which normally cause the rear ends of guide tube42 and 43 to abut bar 51. While springs 68 are shown in Figs. 4 and 6 asbeing connected to brackets 55 and 56, Figs. 1, 2 and 3 show saidsprings attached to arms 57 and 58 for the sake of clarity ofillustration, the functions in both positions being equivalent.

Since latches 57 and 58 are both mounted fast upon rotatable rod 61, therotation of one latch causes the corresponding rotation of the otherlatch. Connected to the upwardly extending arm 71 (Fig. 4) of latch 62is the laterally extending arm 72 of longitudinal pull rod 73 slidablysupported in bracket 74 mounted on the side of press bed 21. The forwardend of rod 73 terminates in an inwardly extending hook 75 which isengageable by finger 76 mounted on carriage 22. Upon forward movement ofcarriage 22, finger 76 engages hook 75 causing rod 73 to move forward inorder to rotate latches 62 and 63 which disengage from hooks 64 and 65,respectively, the purpose of this operation being described hereinbelow.

The sequence of the printing cycle is schematically illustrated in Figs.1, 2 and 3. Fig. 1 shows the apparatus in position at the beginning ofthe cycle prior to impressing a reproduction of the stencil upon thepaper. The paper upon which the design or printing is to be impressed iswrapped around rotary platen 24, and is held thereon in the manner wellknown in the art. Latches 62 and 63 are locked to hooks 64 and 65, andcarriage 22 begins to move forward to the right, as shown in Pig. 3. Atthe same time springs 52 urge bar 51 to the right thereby causing guidetubes 42 and 43, and accordingly, inking assembly 41, to move to theright. Although carriage 22 and frame 26 continue in their longitudinalmotion to the right, inking assembly 41 moves to the right only alimited distance as determined by bar 51 abutting against upwardlyextending bracket 78 mounted on press bed 21. The inking assembly 41 isbrought to rest by this means at a point where the upper edge of thefpaper which is arranged to move at the same velocity as the stencil. Bythis means the squeegee is maintained in the optimum printing positionfor squeezing the ink through the stencil and onto the paper.

After an impression has been printed upon the paper on platen 24 and thelatter has passed out of contact with stencil 36, bar 28 of frame 26comes into engagement with inking assembly 41 and draws the latter andstencil 36 clear of the platen. At the point when the paper has beenprinted, and just prior to, or simultaneously with, the engagement ofbar 28 with inking assembly 41 to draw it to the right, latches 62 and63 are disengaged from hooks 64 and 65 by means of finger 76 engaginghook of pull rod 73. (See also Fig. 4.)

Tube 42 and 43 thereupon slide longitudinally to the right over guiderods 44 and 45 against the action of springs 68. During the returntransit of carriage 22 to the left, at which time no printing takesplace, inking assembly 41 is urged to the left back to its originalposition as shown in Fig. 1, by the independent action of springs 68,during which time finger 76 has released hook 75 on pull rod 73permitting springs 67 to cause latches 62 and 63 to engage hooks 64 and65, respectively, on

bar 51. The rear ends of guide tubes 42 and 43, sliding over rods 44 and45, cause bar 51 to move to the left against the action of springs 52.The machine is now ready to begin another printing cycle.

The inking assembly 41 comprises an elongated container of sheet metal,or the like, having floor 81, front wall 82 and rear wall 83 extendingtransversely within frame 26. See Figs. 7, 8 and 9. Mounted on theforward face of wall 83 is a bracket 84 made of sheet metal, casing orthe like, having a forwardly and upwardly extending guard flange 85terminating in an obliquely upwardly extending lip 86, said bracket,flange and lip extending longitudinally in respect of said inkingassembly. The forward wall 82 of the inking assembly has a downwardlyand rearwardly extending shoulder 87 which is terminated by shelf 88which extends forwardly to the rear face of wall 82.

Positioned within the chamber defined by floor 81, walls 82 and 83,flange 85 and shoulder 87, is an elongated tube 91, made of. a resilientand flexible material such as rubber, neoprene, or the like, and havingan upwardly and forwardly extending longitudinal tongue in the form of asqueegee 92 which is confined slidably in the mouth formed by lip 86 andshoulder 87.

Tube 91 has a pair of apertures 92 along its rear wall which are matchedwith a corresponding pair of apertures 93 and wall 83, through which isconnected a pair of tubes 94, which communicate with an air supply tube95, as shown in Fig. 4. In some embodiments, a single air supply tube 95may communicate directly through wall 83 with the interior of tube 91.Since tube 95 is connected to a pressure and vacuum system, to bedescribed hereinbelow, it is apparent that tube 91 may be inflated ordeflated in accordance with the requirement of causing the upper edge ofsqueegee 92 either to be urged upward against the underside of stencil36 (Fig. 8), or to be retracted therefrom (Fig. 9).

In the embodiment shown in Figs. 7, 8 and 9, guard 85 and lip 86 areprovided for the purpose of limiting the expansion of tube 91 when airor gas is introduced therein under pressure, since the tube may be madeof uncorded rubber or similar elastic material. Tube 91 mayalternatively be made of corded rubber which would limit its expansionunder pressure, in which event guard 85 and lip 86 may be dispensedwith.

Mounted on the rear face of wall 83 of inking assembly 41 is anelongated ink duct 97 having a plurality of apertures 98 which registerwith corresponding apertures 99 and 101 in wall 83 of bracket 84,respectively. Said apertures permit ink from the duct to flow into theink assembly 41 and over flange 85 which also has a plurality ofapertures 102 which permit ink 103 to flow down on to the upper surfaceof tube 91, particularly when the latter is deflated. (Fig. 9.) Althoughperforations 102 may be omitted in flange 85, these perforations aredesirable in some embodiments in order to wet the upper surface of tube91 with ink so that a portion thereof may be carried upwards with thesqueegee adjacent the inner surface of lip 86. Communicating with theinterior of duct 97 is an ink supply tube 108 which extends rearwardlyof the machine through bar 23 of frame 26, the rear end of said tubebeing connected to a flexible hose 109 which leads to an ink supplyreservoir, not shown.

The rear end of air supply tube 95, which also extends through bar 28 offrame 26, is connected to one end of flexible hose 111, the other end ofwhich is attached to inlet tube 112 positioned on one side of valve box113 and communicating with the valve chamber 114 therein. Valve box 113is shown in plan view in Fig. 4, and in enlarged schematic cross sectiondetail in Figs. and ll.

On another side of valve box 113 are pressure inlet tube 115 and exhaustoutlet tube 116 communicating with the valve chamber 114. Inlet pressuretube 115 is connected by suitable means, not shown, to pressure line117, connected in turn to pressure tank 118. Exhaust outlet tube 116 isconnected by suitable means, not shown, to exhaust line 119, connectedin turn to exhaust tank 120. Pressure tank 118 and exhaust tank 120 areeach connected by way of suitable check valves 123 and 124,respectively, to a pumping mechanism 125 operated by motor 126. Motor126 is connected to a suitable power source by way of lead lines 127 and128. Connected in series in lead line 127 is an electric pressure meter131 whose pressure sensitive element communicates with the interior oftank 118. Meter 131 is adjusted automatically to close or break thecircuit in lead line 127 controlling motor 126 in accordance withdesired gas pressure within predetermined limits in tank 118. Checkvalves 123 and 124 serve as limit controls upon the respective pressuresin tank 118 and tank 120 in a manner well known in the art.

The alternate inflation and deflation of tube 91 first urges squeegee 92against stencil 36 during the printing pass of frame 26; and thendeflates said tube, retracting the squeegee during the non-printingreturn pass of the frame. This is accomplished by providing withinchamber 114 of valve box 113, a valve block 131 having a pressurepassage 132 and an exhaust passage 133 that are spaced apart a lesseramount than the distance between pressure inlet 115 and exhaust outlet116.

Valve block 131 is movable longitudinally within valve box 113 and whenpressure passage 132 registers with pressure inlet 115, exhaust outlet116 will be shut off by the mass of block 131 (Fig. 10). Alternatively,when exhaust passage 133 registers with exhaust outlet 116, pressureinlet 115 will be shut off in like manner (Fig. 11).

Both passages 132 and 133 communicate with an elongated recess 134 inthe upper surface of block 131, which in turn communicates with valveinlet 112 regardless of the position of said block within chamber 114.Thus, the longitudinal movement of block 131 in one direction or theother will provide a differentiation between the pressure portion andthe exhaust portion of the pumping system.

Connected to the rearward end of valve block 131 is rod 137 whichextends slidably through end cap 138, threadably mounted over the end ofvalve box 113. Rod 137 extends slidably through support bracket 139mounted on press bed 21 and is terminated by laterally extending finger141 which is engaged by bar 51 as the latter moves rearwardly. Connectedto the forward end of valve block 113 is rod 143 which extends slidablythrough the end wall of valve box 113, and extends slidably through apair of support brackets 144 mounted on press bed 21, and is terminatedby laterally extending finger 145 which is engaged by bracket 146mounted on frame 26.

When carriage 22 has moved to a point just short of its forwardrnostposition after the printing pass, as shown in Fig. 2, bracket 146engages finger 145 and causes it to move rod 143 forward, whereby valveblock 131 is also moved forward to a point where exhaust line 119 is incircuit with tube 91 of the squeegee mechanism. See Fig. 11. Tube 91 isthereby deflated causing retraction of squeegee 92 from stencil 36 (Fig.9), at which time carriage 22 begins its reward motion to its startingposition in Fig. l.

During the transit of carriage 22 to its starting position, valve block131 remains in its evacuating position until the carriage reaches apoint just short of the starting position, at which time bar 51, moved.rearwardly by guide tubes 42 and 43, engages finger 141, which nowcauses rod 127 to pull valve block 131 into the pressure position asshown in Fig. 10. At this time tube 91 is inflated (Fig. 8), causingsqueegee 92 to rise and be urged against screen 36 during the entireprinting pass of the machine, as described hereinabove.

The locations of fingers 141 and 145 on rods 137 and 143, respectively,relative to bar 51 and bracket 146, respectively, are arranged toprovide an alternation of the valving mechanism between the pressurecondition and evacuating condition for operating squeegee 92 insynchronized timing with the pass of stencil 36 past platen 24 duringthe printing and non-printing portions of the cycling action of themachine. Fingers 141 and 145 may be adjusted on rods 137 and 143,respectively, in different positions thereon for accommodating thealternation of the pressure-exhaust system with stencils 36 and/ orframes 26 of varying sizes which might require different timing cycleson the part of the inking mechanism.

It will be noted that normally there is a slight clearance between theperiphery of the paper mounted on platen 24 and stencil 36 on frame 26whereby the plane of the stencil is ordinarily spaced apart from theperiphery of platen 24 and of the paper wrapped around it. In previousmechanisms, various mechanical arrangements are required to urge thestencil 36 against the paper on platen 24 by means of an inking rolleror squeegee, said arrangements being subject to mechanical failure aswell as manifesting lack of uniformity of impression across the wholewidth of the paper to be printed.

In the apparatus of the present invention, however, mechanicalexpedients for lifting the squeegee to urge the stencil against theplaten have been completely eliminated, and there has been substitutedthe extremely simple inflatable squeegee which has no mechanical partsto get out of order, and which provides a uniform pressure along thewhole width of the stencil to impress sharply defined reproductions uponthe paper on platen 24. During the return pass of the stencil when noprinting takes place, the simple deflation of the squeegee permits thestencil to bypass the platen without the danger of accidental transferof ink to the platen.

An alternative embodiment for an inking and squeegee mechanism is shownschematically in Figs. 12, 13, 14 and 15. In this embodiment, the wholeframe 26 serves as a reservoir containing the ink, and the squeegeeassembly, which extends laterally within said frame, is movablelongitudinally therein by suitable means, not

shown, which are comparable to the means shown in mounted on a pluralityof rails 152 which slide longicessive expansion of the tube.

tudinally on floor 31 of frame 26. Mounted by means of hinges 153 toplatform 151 are a plurality of ramps 154 which extend downwardly intothe pool of ink 155. Mounted by suitable means on platform 151 is aflexible squeegee tube 156 having a plurality of longitudinal ridges 157(Figs. 12, 13 and 14). Communicating with the interior of tube 156 is anair supply tube 158, comparable in function to tube 95 (Fig. 4), andconnected by suitable means not shown, to valve box 113.

Tube 156 may be inflated (Fig. 13), in the manner described hereinabove,causing ridges 157 to be urged upwards against the underside of stencil36, or it may be deflated (Fig. 14), thereby retracting the ridges fromthe stencil. While the squeegee assembly moves in a direction oppositeto floor 31 during a portion of the ncnprinting transit thereof, ink iscaused to rise on ramps 1.54 and to flow onto the ridges 157 of deflatedtube 156, as shown in Fig. 14.

In this manner, the ridges are provided, during the non-printing pass ofthe machine, with a supply of ink which is retained in said ridges untilthe printing pass of the machine is instituted, as in Fig. 3, andsqueegee is inflated. Here again, as in the previous embodiment, auniform pressure is maintained along the whole length of thesqueegee,-thereby providing a sharp definition of the printingimpression along the whole width of the print.

In the embodiment shown in Figs. 12 through 15, ink is supplied to theink reservoir on floor 31 of frame 26 by Way of an ink duct 161 havingone or more outlet apertures 162. Ink duct 1&1 is supported by a bracket153 which is attached by means, not shown, to a suitable portion of themachine. Ink duct 161. has a supply tube 164 which leads to an inkreservoir (not shown). The feeding of ink to duct 161 as well as to inkduct 97 (Figs. 1, 2, 3) may be provided by suitable pressure of gravitymeans as the circumstances require.

It will be understood that Where a squeegee tube 156 of the type in Fig.12 is used, it is preferably made of a corded rubber or the like, whichwould prevent any ex- It is apparent that the ridged squeegee tube 156may be substituted for tube 91 and squeegee 92 in the embodiment shownin Fig. 7.

In some embodiments, squeegee tubes 91 and 156 may be made of a materialthe structure and constitution of which cause it to maintain theoperative edge of the squeegee normally retracted from stencil 36, inwhich case it is unnecessary to provide for an exhaust branch in thepumping system. In these circumstances, only a pressure pumping systemneed be utilized, with a suitable relief valve 167 (Fig. 4), well knownin the art, being inserted into pressure line 95 for permitting thesqueegee tube to retract when the pressure circuit is closed by valveblock 131 during the return pass of carriage 22.

In the specification, I have explained the principles of my invention,and the best mode in which I have contemplated applying thoseprinciples, so as to distinguish my invention from other inventions; andI have particularly pointed out and distinctly claimed the part, mode orcombination which I claim as my invention or dis covery.

While I have shown and described certain preferred embodiments of myinvention, it will be understood that modifications and changes may bemade without departing from the function and scope thereof, as will beclear to those skilled in the art.

I claim:

1. A stencil printing machine comprising means for forcing inkthroughthe stencil and being in the form of a tube of flexible material,a longitudinal portion of said tube being in the form of a squeegee,means for inflating the tube to cause the squeegee to be urged againstthe stencil when said squeegee moves in one direction relative to saidstencil, and means for relieving pressure within the tube to cause thesqueegee to be retracted completely from the stencil when said squeegeemoves in the opposite direction relative to said stencil.

2. A stencil printing machine according to claim 1, and furthercomprising a stencil, a carriage upon which said stencil is mounted,means for producing reciprocating motion upon said carriage, and meanson said carriage for operating the inflating and relieving means intimed relation to the motion of said carriage.

3. A stencil printing machine comprising means for forcing ink throughthe stencil and being in the form of a tube of flexible material, alongitudinal portion of said .tube being in the form of a squeegee, aplurality of longitudinal ridges on the squeegee portion of the tube,means for inflating the tube to cause the ridges to be urged against thestencil when said squeegee moves in one direction relative to saidstencil, and means for deflating said tube to cause the ridges to beretracted completely from the stencil when said squeegee moves in theopposite direction relative to said stencil, said ridges being adaptedto be supplied with ink when said tube is deflated.

4. A stencil printing machine according to claim 3 wherein said tube iscomposed of corded resilient material, the cording therein being adaptedto limit the expansion of the tube.

5. A stencil printing machine comprising a carriage adapted forreciprocating motion, an inking assembly mounted transversely on saidcarriage and movable longitudinally therein and independently ofportions of the motion of said carriage, means for maintaining saidinking assembly motionless during a portion of the motion of saidcarriage during the printing operation, a stencil mounted on saidcarriage over said inking assembly, a squeegee in said inking assembly,said squeegee having the form of a flexible tube, means for inflatingsaid tube to urge a longitudinal surface portion thereof against thestencil when said portion moves in one direction relative to saidstencil and means for deflating said tube in order to retract saidportion completely from said stencil when said portion moves in theopposite direction relative to said stencil.

6. Apparatus according to claim 5 wherein the carriage has a forwardtransit and a return transit, the printing operation taking place onlyduring the forward transit, and further comprising means for inflatingthe tube during the forward transit of said carriage, and means fordeflating said tube during the return transit of said carriage.

7. A stencil printing machine comprising a carriage adapted forreciprocating motion, a stencil mounted on said carriage, a rotaryplaten mounted transversely above said carriage, said stencil beingnormally spaced apart slightly from the periphery of said platen, aninking assembly mounted transversely on said carriage underneath saidstencil and movable longitudinally therein, a squeegee on said inkingassembly, said squeegee having the form of a flexible tube, means forinflating said tube whereby said squeegee causes the stencil to be urgedagainst the rotating platen during the printing pass of said carriage,and means for deflating said tube in order to retract said squeegee andto permit the stencil to resume its spaced apart condition from theplaten during the return pass of the carriage.

8. A machine according to claim 7, and further comprising means formoving the squeegee independently of the motion of said carriage, andmeans for maintaining said squeegee motionless during the printing passof the the carriage.

9. A machine according to claim 7 wherein said tube is made of cordedrubber whereby the expansion of said tube is limited.

10. A machine according to claim 7, and further comprising means mounted011 said inking assembly adjacent said tube and adapted to limit theexpansion thereof.

11. In a stencil printing machine having a carriage adapted forreciprocating motion and a stencil on said carriage, an inking mechanismcomprising a frame positioned transversely of said carriage and movablelongitudinally therein on one side of said stencil, a flexible tubemounted longitudinally in said frame, a longitudinal squeegee mounted onsaid tube, means for inflating said tube to urge said squeegee againstthe stencil when said squeegee moves in one direction relative to saidstencil, and means for deflating said tube for retracting said squeegeefrom said stencil when said squeegee moves in the opposite directionrelative to said stencil.

12. A machine according to claim 11, and further comprising ;a guardlongitudinally mounted in said frame adjacent said tube and adapted tolimit the expansion thereof.

13. A machine according to claim 11, and further comprising a flange onsaid frame forming a mouth therewith through which said squeegeeprotrudes, said mouth being adapted to guide the movement of saidsqueegee between its printing position and its retracted position.

14. A machine according to claim 11, and further comprising a flangeconnected within said frame extending over a portion of said tube tolimit the expansion thereof, and a plurality of apertures in said flangefor permitting ink to flow onto the squeegee.

15. A stencil printing machine comprising a carriage adapted forreciprocating longitudinal motion, a stencil mounted on said carriage, aflexible tube mounted transversely in said carriage and movablelongitudinally relative to said stencil and said carriage, a squeegeeedge on said tube normally retracted from said stencil, means connectedto said tube and adapted to inflate the tube to cause the squeegee to beurged against said stencil as the latter moves past said squeegee in onedirection, and means relieving the pressure in said tube to permit saidsqueegee to be retracted from said stencil during the opposite motion ofsaid stencil.

References Cited in the file of this patent UNITED STATES PATENTS

